07-20-2014, 05:21 PM
It is possible, although not too comfortable, to interact with the UI in the plugins - you can catch the PLAYER_USING_BLOCK hook and let it cancel the action, then let it simulate the chest opening by itself - Lua can open any kind of UI window with any items, using the cLuaWindow class. That one provides the callbacks you need that MCS calls when the player clicks inside the window.